Popping and unstable boost!

[REBEL GT TURBO]

Right ive just fitted a new (second hand) carb and the car is running again:)
Its idling perfect 14.1/14.2 when driving round normal its staying around 14.2 ish but when in boost its holding back and sometimes making a popping noise:confused: also the AFR isnt dropping its staying in the 14's!!

How do i go about setting up the carb?? do i just play around with the mixture jet screw to balance it out?? all the jets are standard but the carb was setup on a gtt with a modified cam!

Any advice would be great!

cheers

[Tony Walker]

popping on boost sounds more like an ignition problem? overboost wiring fault, large plug gap? leads arcing? dizzy cap/rotor arm worn?

[REBEL GT TURBO]

popping on boost sounds more like an ignition problem? overboost wiring fault, large plug gap? leads arcing? dizzy cap/rotor arm worn?


Fitted brand new ngk plugs...should they need the gaps setting?? Fitted brand new dizzy and rotor arm yesterday!

[Tony Walker]

Gaps should be checked before fitting, even roughly by eye, they can get bashed about. but i doubt this is your fault if the fault was there before you changed the plugs. do you still have overboost sensor fitted, what boost pressure do you run too?

[Brigsy]

Is the carb plumbed in properly? stick some pics up. Afr's are far too lean on boost, take it steady until you get it sorted:crap:

[REBEL GT TURBO]

ok what should the gaps be on the plugs? Ill get a gap setter tonight and check em! Im gonna look at the fuel filter on the carb see if there is any s**t in there! Also if i close the grub screw on the idle jet then turn it until its idling smooth do i then need to set this to get the mixture of air and fuel correct when driving and on boost??

[Brigsy]

The idle jet should be tight into the carb body & adjust the mixture screw to suit.

The mixture screw doesnt affect on boost fuelling, only idle.

[olidaviesuk]

Need to sort the basics out first or will be running round in circles. Couple of hours work but worth it in the long run.

1. Check boost circuit for any leaks, cracked pipes etc

2. Put boost circuit back to completely standard (Inc actuator rod length) plenty of posts on how to do this and manual is in the archive section.. (can always change after but for fault finding is invaluable) If you're running anything more than a standard T2 turbo then setup the boost circuit with the cup mod - however, you want to be running no more than 12-13psi and I would jet the carb a/c 0.9mm and main 1.45 to be on the very safe side)

3. Check the valve clearances .2 inlet .25 ex (mm) off the top of my head , could be other way round tho..,

4. Check and gap your plugs .8mm is what the book says, again off the top of my head, check against the book.. Check leads for any cracks splitting etc..

5. Check aei vacumn capsule by blowing into it - again plenty of posts if you do a quick search....

6.... Important bit, rejet the carb, this is prob far too rich for some, but again not likely to lean out under standard boost... A/c 1mm jet, main 1.35mm with 5mm sticking out the accelerator jet rod, really good post in the archive about rejecting, rebuilding ur carb...

After all this, should be pulling well with none of the previous symptoms, albeit with a fair bit of black smoke out the back coming on boost..

Best o' luck

Oli

Forgot to add, if this doesn't fix, then leads, tdc sensor and aei unit are all on the suspect list, also from the front - the boost control parts of the carb - the long bit should be towards the back of the carb(on the right-from front of car) and the short bit towards the front, its not been unheard of for them to be put back together incorrectly - again plenty o' pics on here to check against....

[REBEL GT TURBO]

cheers oli ;)